Injection molding machine

ABSTRACT

An injection molding machine including a shot cylinder which is indexed between an inject and shot preparation position, the cylinder in the latter position having forced therein under high pressure the plastic material forming the shot.

United States Patent Schwartz 1 51 ar. 21, 11972 54] INJECTION MOLDINGMACHINE 2,477,258 7/1949 MacMillin ....18/30 F] 2,479,383 8 1949 M M'11'[72] Inventor: William H. Schwartz, University Heights, ac l m 18/30 F]Ohio FOREIGN PATENTS OR APPLICATIONS 1 Assigneel Lester Engin ri g p y,Cleveland, 1,118,166 3/1956 France ..18/30 AP Ohio 1,195,860 5/1958France ..18/30 AA [22] Flled: 1969 Primary ExaminerRobert D. Baldwin[21] Appl.No.: 793,838 AssistantExaminer--Michael0. SuttonAttorney-Oberlin, Maky, Donnelly & Renner [52] US. Cl ..425/243,425/245, 425/247 57 A [51] Int Cl ..B29f1/02 1 BSTRACT [58] Field ofSearch 1 8/30 AA, 30 AC, 30 AM, 30 AP, 18/30 AR, 30 AS, 30 G, 30 Q, 30QM, 30 QQ, 30 RV, 30 RM, 30 WT, 30 WI, 30 WR, 30 F] [56] ReferencesCited UNITED STATES PATENTS 2,239,338 4/1941 Norelli ..18/30 RV Aninjection molding machine including a shot cylinder which is indexedbetween an inject and shot preparation position, the cylinder in thelatter position having forced therein under high pressure the plasticmaterial forming the shot.

7 Claims, 3 Drawing Figures Patented March 21, 1972 2 Sheets-Sheet 1INVENTOR W/LL l/M I H. SCHWARTZ 9 Y m nawwwf Patented March 21, 19723,650,654

2 Sheets-Sheet 2 INVENTOR W/LL/AM H. SCHWARTZ ATTORNEYS INJECTIONMOLDING MACHINE This invention relates generally as indicated to aninjection molding machine and more particularly to a machine for theefficient molding of hard to mold materials such as polyestersreinforced with fiber glass.

Such hard to mold materials normally cannot be sent through a screw andmust be prepared in batches having limited bench life.

It is accordingly a principal object of the present invention to providea machine having particular utility in the molding of hard to moldmaterials such as polyesters having fiber glass therein.

Another principal object is the provision of such machine utilizing ashot cylinder which can beindexed between a shot inject and a shotpreparation position.

A further object is the provision of such machine wherein a plasticmaterial is forced into the shot cylinder under high pressure in theshot preparation position of the latter.

Still another object is the provision of a simplified and efficientmachine for economically forming parts of hard to mold plastics such asfiber glass reinforced polyesters.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail a certain illustrativeembodiment of the invention, this being indicative, however, of but oneof the various ways in which the principles of the invention may beemployed.

In said annexed drawings:

FIG. I is a fragmentary view of an injection molding machine partiallybroken away and in section in accordance with the present inventionshowing the shot cylinder in the shot preparation position;

FIG. 2 is a view similar to FIG. 1 showing the shot cylinder indexed 90prior to the institution of the shot; and

FIG. 3 is a view similar to,FIGS. l and 2 showing the completion oftheshot.

Referring now to FIG. 1, it will be seen that the machine includes afixed die platen l and a movable die platen 11, the latter being mountedfor movement along tie bars 12 by a clamping mechanism, not shown. Suchtie bars may be four in number. The movable platen 11 may be movedtoward and away from the fixed platen I0 and clamped in mold closedposition by the mechanism seen, for example, in applicants copendingapplication, Ser. No. 781,552, filed Dec. 5, 1968, entitled InjectionMolding Machine, and now U.S. Pat. No. 3,588,957.

A mold half or die 14 is mounted on the fixed platen and cooperates witha mold half or die 15 mounted on the movable die platen II. The twocooperate to form a mold cavity shown generally at 16. The movable dieplaten includes an ejector mechanism 17 which includes ejector pins 18which are extended when the mold is opened to discharge the finishedproduct from the movable mold half 15.

The fixed mold half 14 includes a cylindrical insert 20 aligned withslightly larger cylindrical insert 21 mounted in the fixed die platen l0and extending into shot frame 22 mounted on the shot end of the machine.The cylindrical members 20 and 21 have axially aligned cylindricalpassages therein shown at 23 in communication with runner 24 leading tothe mold cavity 16.

Journaled generally centrally within the shot frame 22 is a shot wheelmember 26 which includes, extending diametrically therethrough, a shotcylinder 27. The shot cylinder may include heating elements 28surrounding the same to facilitate the plasticizing of the plasticmaterial M therewithin. The wheel 26 may include oppositely projectingtrunnions journaled within opposite sides of the frame 22 and on onesuch trunnion there is provided a pinion 29 in mesh with rack 30reciprocated by the rod 31 of double-acting piston-cylinder assembly 32mounted on bracket 33 secured to the frame 22.

The wheel 26 may include a laterally projecting stop rod 35 whichengages inwardly projecting stops 36 and 37 in alternate positions ofthe wheel.

The top of the frame 22 includes a relatively large diameter cylindricalchamber 40 into which the plastic material M is introduced. Suchcylindrical chamber at its lower end includes a conical surface 41, theapex of which terminates in cylindrical passage 42 passing centrallythrough inwardly directed projection 43 in the frame 22.

The cylindrical chamber 40 receives a large diameter squeeze piston 45,the cylinder assembly of which may be mounted on the frame plate 46. Thepiston exerts a substantial amount of pressure on the plastic material Mwithin such chamber.

The passage 42 is aligned with passage 47 in the bottom of the frame 22which extends upwardly through inwardly extending projection 48. Mountedfor reciprocation in the passage 47 is a backup plunger 50. The backupplunger 50 is connected to the piston 51 of piston-cylinder assembly 52mounted on the bottom of the frame 22. The tip 53 of the backup plunger50 in its retracted position just clears the wheel 26 as seen in FIG. 2.

Diametrically opposite the passage 23 in the cylindrical members 20 and21 is a bushing 54 supporting injection plunger 55 which is actuated bypiston-cylinder assembly 56. When the tip 57 of the injection plunger isretracted, it will just clear the wheel 26 as indicated in FIGS. 1 and2.

In FIG. I, the wheel 26 has been indexed to place the shot cylinder 27in a vertical position aligned with the passages 42 and 47. This isaccomplished by retraction of the rack 30 and the engagement of the stop35 against the stop 36. A charge of plastic material is placed withinthe chamber 40 and the high pressure ram is brought down to close thetop of the chamber. The backup piston is extended until the tip 53 ofsuch backup plunger is in the approximate position seen in FIG. 1. Theram 45 is now brought down forcing the plastic material under highpressure through the passage 42 and into the shot cylinder 27. Thepressure created by the ram 45 will cause the backup plunger 50 to backoff or retreat. This may be accomplished by bleeding hydraulic fluidfrom the blind end of the cylinder 52. In any event, the plasticmaterial is placed under high pressure between the ram 45 and the backupplunger 50. While the shot is thus being prepared and plasticized, bothby the pressure exerted thereon and the heat obtained from the heatingelements 28, the mold closing mechanism will move the molds intojuxtaposition as seen and a clamping force will be exerted thereon.

Referring now to FIG. 2, when the tip 53 of the backup plunger is in theposition shown, the wheel 26 is now indexed in the direction of thearrow 60 aligning the shot cylinder 27 and the plastic charge 61 thereinwith the passage 23 on the one hand and the shot plunger on the other.Indexing of the wheel is accomplished by extension of thepiston-cylinder assembly 32 placing the stop 35 now against the stop 37.The tip 53 of the backup plunger 50 must, of course, clear the wheel andbe in the position seen in FIG. 2.

Referring now to FIG. 3, it will be seen that the injection or shot ramis now extended passing through the shot cylinder within the wheel andinto the passage 23 filling the mold cavity 16. The shot ram is thenretracted until the tip 57 clears the wheel as seen in FIG. 2 and thewheel may then be indexed back to the position seen in FIG. 1 so thatthe shot cylinder 27 is in position to receive another shot or charge ofplastic material. The backup plunger 50 will be extended until its tip53 is in the position shown in FIG. 1 and the large ram 45 is thenutilized to prepare another shot within the shot cylinder within thewheel 26. While the shot is being prepared, the completed mold may beremoved from the separable mold halves.

It can now be seen that there is provided an injection molding machineand method wherein the shot cylinder is indexed from a shot preparationposition to a shot inject position, the shot cylinder when thus indexedbeing aligned with the shot plunger.

I, therefore, particularly point out and distinctly claim as myinvention:

1. An injection molding machine comprising a pair of separable dieholders adapted to support a pair of separable dies, an indexablemember, a shot cylinder, a shot preparation means, a shot plunger, andmeans in said member to index said member and thus said cylinder from ashot preparation and reception position to a shot inject position andvice versa, said member being supported for rotation about an axispassing through said shot cylinder, the shot preparation means includinga high pressure ram and a backup plunger that are in com munication withsaid cylinder in the shot preparation and reception position, the backupplunger being aligned with and positioned in the cylinder before shotinsertion and being driven out of said cylinder during insertion by saidram compressing plastic material against said plunger and concurrentlyforcing such material into said cylinder, the cylinder in said injectposition being in communication with such separable dies and alignedwith said shot plunger.

2. An injection molding machine as set forth in claim 1 wherein saidshot preparation means further includes heating means surrounding saidcylinder.

3. An injection molding machine as set forth in claim 1 wherein saidbackup plunger is connected to the piston of a piston-cylinder assembly,the compressive pressure exerted on said material being controlled atselected magnitudes by bleeding hydraulic fluid from the cylinder whensuch pressure magnitudes obtain.

4. An injection molding machine as set forth in claim 1 wherein saidcylinder is supported by a wheel member which is rotated to index saidcylinder.

5, An injection molding machine as set forth in claim 1 including a rackand pinion drive operative to index said cylinder, said rack beingoperated by a double acting pistoncylinder assembly.

6. An injection molding machine as set forth in claim 1 wherein saidcylinder is adapted to be pivotally moved and said indexing means pivotssaid cylinder approximately between said positions.

7. An injection molding machine as set forth in claim 1 wherein saidindexing means moves said cylinder to a vertical orientation in saidpreparation and reception position and to a horizontal orientation insaid inject position.

1. An injection molding machine comprising a pair of separable dieholders adapted to support a pair of separable dies, an indexablemember, a shot cylinder, a shot preparation means, a shot plunger, andmeans in said member to index said member and thus said cylinder from ashot preparation and reception position to a shot inject position andvice versa, said member being supported for rotation about an axispassing through said shot cylinder, the shot preparation means includinga high pressure ram and a backup plunger that are in communication withsaid cylinder in the shot preparation and reception position, the backupplunger being aligned with and positioned in the cylinder before shotinsertion and being driven out of said cylinder during insertion by saidram compressing plastic material against said plunger and concurrentlyforcing such material into said cylinder, the cylinder in said injectposition being in communication with such separable dies and alignedwith said shot plunger.
 2. An injection molding machine as set forth inclaim 1 wherein said shot preparation means further includes heatingmeans surrounding said cylinder.
 3. An injection molding machine as setforth in claim 1 wherein said backup plunger is connected to the pistonof a piston-cylinder assembly, the compressive pressure exerted on saidmaterial being controlled at selected magnitudes by bleeding hydraulicfluid from the cylinder when such pressure magnitudes obtain.
 4. Aninjection molding machine as set forth in claim 1 wherein said cylinderis supported by a wheel member which is rotated to index said cylinder.5. An injection molding machine as set forth in claim 1 including a rackand pinion drive operative to index said cylinder, said rack beingoperated by a double acting piston-cylinder assembly.
 6. An injectionmolding machine as set forth in claim 1 wherein said cylinder is adaptedto be pivotally moved and said indexing means pivots said cylinderapproximately 90* between said positions.
 7. An injection moldingmachine as set forth in claim 1 wherein said indexing means moves saidcylinder to a vertical orientation in said preparation and receptionposition and to a horizontal orientation in said inject position.